maynard writes: "Scientists from Johns Hopkins University School of Medicine and Howard Hughes Medical Institute working in collaboration have published a study in the peer reviewed journal Science showing that mice transgenetically altered with a single human gene are then able to see in full tri-color vision. Mice without this alteration are normally colorblind. The scientists speculate that even mammalian brains from animals that have never evolved color vision are flexible enough to interpret new color sense information with just a simple addition of new photoreceptors. Such a result is also indicated by a dominant X chromosome mutation that allows for quad-color vision in some women. From the article:

The experiments were designed to determine whether the brains of the genetically altered mice could efficiently process sensory information from the new photoreceptors in their eyes. Among mammals, this more complex type of color vision has only been observed in primates, and therefore the brains of mice did not need to evolve to make these discriminations.

The new abilities of the genetically engineered mice indicate that the mammalian brain possesses a flexibility that permits a nearly instantaneous upgrade in the complexity of color vision, say the study's senior authors, Gerald Jacobs and Jeremy Nathans.